This SAE Information Report is a summary comparison of existing protocols found in manufacturing, automotive, aviation, military, and computer applications which provide background or may be applicable for Class C application. The intent of this report is to present a summary of each protocol, not an evaluation. This is not intended to be a comprehensive review of all applicable protocols. The form for evaluation of a protocol exists in this paper and new protocols can be submitted on this form to the committee for consideration in future revisions of this report. This report contains a table which provides a side-by-side comparison of each protocol considered. The subsequent section provides a more detailed examination of the protocol attributes. Many of the protocols do not specify a method for one or more of the criteria. In these circumstances 'under defined' or 'not specified' will appear under the heading. Certain protocol specifics or details are omitted for the sake of brevity. Every attempt is made to provide the interest reader with the necessary references for further research.